The use of cleaning blades is widely practiced in electrostatographic printers and copiers for the removal of toner particles from various moving surfaces (Seino et al. J. Imag. Sci. & Tech. 2003, Vol. 47, 424). The portion of the cleaning blade that contacts the surface to be cleaned is generally a polyurethane because such polymers are durable and have a high degree of resilience that is well suited for making contact with a smooth surface.
The use of cleaning (wiper) blades for cleaning webs is described in U.S. Pat. No. 6,453,134 (Ziegelmuller et al.) where the cleaning blades are used to clean transport webs in electrophotographic printers. Toner patches are removed from the transport webs after image density is measured with some type of radiation such as a light emitting diode (LED).
The properties of such cleaning blades can be improved by surface coatings over the polyurethane. For example, U.S. Pat. No. 5,363,182 (Kuribayashi et al.) describes the use of a surface coating of graphite particles in a nylon resin. A primer layer is used to enhance the adhesion of the graphite-containing nylon resin to the polyurethane blade.
Urethane polymers that are designed to be hard like a ceramic yet flexible like a polymer are part of a group of materials known as ceramers. As discussed in U.S. Pat. No. 5,968,656 (Ezenyilimba et al.), ceramers are coated as layers of approximately 5 micrometers on relatively thick, resilient polyurethane substrates or cushion “blanket” cylinders to provide transfer of toner from a photoreceptor to a receiver in electrophotographic printers. One ceramer composition has a urethane backbone made from isophoronone diisocyanate and a polyether diol wherein the backbone is branched by the addition of trimethylolpropane and 1,4-butane diol serves as a chain extender, and the branched urethane is endcapped with 3-isocyanatopropyltriethoxysilane to provide alkoxysilane groups that can react with alkoxysilanes in a sol-gel reaction to form a polyurethane silicate hybrid organic-inorganic composite (OIC) network ceramer.
Urethane polymers containing fluorinated substituents are known. One mode of introduction of the fluorinated component is from a fluoroether, either as an endcapper or from the diol into the polyurethane backbone. U.S. Patent Application Publication 2007/0244289 (Tonge) describes a method of making urethane based fluorinated monomers that can be used to prepare radiation curable coating compositions, and discloses that such monomers can be used to formulate a ceramer composition such as disclosed in U.S. Pat. No. 6,238,798 (Kang et al.) that describes ceramer coating compositions comprising colloidal inorganic oxide particles and a free-radically curable binder precursor which comprises a fluorochemical component that further comprises at least two free-radically curable moieties and at least one fluorinated moiety. In such compositions, the colloidal inorganic oxide particles can be surface treated with a fluoro/silane component that comprises at least one hydrolysable silane moiety and at least one fluorinated moiety. As discussed therein, aggregation of the inorganic oxide particles in such compositions can result in precipitation of such particles or gelation of the ceramer composition, which, in turn, results in a dramatic, undesirable increase in viscosity.
Copending and commonly assigned U.S. Ser. No. 12/713,205 (filed Feb. 26, 2010 by Ferrar, Rimai, Miskinis, and DeJesus) describes cleaning blades having a polymer substrate and fluorinated polyurethane ceramer coatings that provide increased surface modulus with a low surface energy coatings. These improved cleaning blades represent an important advance in the art, but there is a desire to improve cleaning blades with lower surface coefficient of friction and greater durability (longer wear). Moreover, there is a need for cleaning blades with polyurethane substrates to which low coefficient of friction coatings can be applied without intermediate adhering layers, and which cleaning blades can be used for either scraping or wiping in electrostatographic apparatus.